The demand for mobile data and voice communication continues to evidence significant growth. Examples for mobile communication systems include cellular-based wireless communication networks. Such networks include various network nodes. The network nodes may include base stations which respectively provide coverage for a radio cell.
A user equipment of a mobile communication network may be a Proximity Service (ProSe) enabled device. Several ProSe enabled user equipments which are located in proximity to each other are operative to perform device-to-device (D2D) communication. D2D communication allows user equipments of a mobile communication network to directly communicate with each other when the user equipments are located in proximity to each other. D2D communication has a wide variety of applications, including public safety and other use cases. Emergency calls are one example for public safety use cases of D2D communication. Direct data or voice communication between user equipments is another example for use cases of D2D communication. For illustration, ProSe enabled user equipments located in proximity to each other may engage in data or voice communication.
In order to perform D2D communication, a user equipment must be capable of detecting one or several other user equipments which are located in proximity to the user equipment. The resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the D2D discovery may be allocated to the user equipment by a base station. Similarly, the resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the D2D communication may be allocated to the user equipment by a base station.
Various techniques may be used for allocating resources for D2D discovery and/or D2D communication. The base station may allocate resources for the D2D discovery and/or for the D2D communication in a manner which is not specific to a particular user equipment, e.g. by broadcasting the information on the allocated resources to a group of user equipments.
At least for some use cases, it is attractive to allocate resources on a peruser-equipment basis. I.e., the D2D resources are allocated specifically to each user equipment. Examples for such use cases are D2D discovery and communication at advertisement points, e.g. at a mall or a retail shop, D2D discovery and communication at vending machines, or other commercial or public safety use cases.
When the resources are allocated to a user equipment (UE), e.g. using a per-UE basis in which different resources are allocated to different UEs, it may be difficult for a mobile communication network to keep control over the usage of the allocated resources when the UE enters an idle mode. For illustration, the mobile communication network conventionally does not have any knowledge on whether and when the allocated resources may be released again after a UE enters the idle mode.